The “no true Scotsman” Fallacy

Subcategory of the Fallacies of Presumptions and could be considered a sub-category of Begging the Question
The fallacy is committed when someone attempts to protect his claim from counter-argument by defining a term in a biased way (which begs the question). The fallacy begs the question by simply defining a true Scotsman in such a way that the claim is assumed to be true. It amounts to saying “A true Scotsman does not put sugar on his porridge, because otherwise, he wouldn’t be a true Scotsman“. Since the premise and conclusions are equivalent, the argument begs the question. For example:

E = “No scientists believes that God created in six days”
C = “The scientists at Answers in Genesis believe God created in six days”
E = “Well, no real scientist believes that God created in six days”

Both the above arguments commit the “no true Scotsman fallacy“. We could equally well say, “Actually, no real scientist believes in evolution. And no reputable journal would publish an evolutionary paper”